1. Field of the Invention
The present invention relates to a method for producing magnetic particles usable in a magnetic recording medium, an MRAM or the like, and more particularly to a method for producing nanoparticles of magnetically hard ordered alloy phase.
2. Description of the Related Art
In order to increase the density of magnetic recording, a reduction in particle size is essential. For example, in a magnetic recording medium widely used, for example, in a video tape, a tape for a computer or a disk, the noise level becomes lower with a reduction in the particle size for a given mass of the ferromagnetic material.
A CuAu or Cu3Au type magnetically hard ordered alloy is a promising material for increasing the magnetic recording density since it has a high magnetocrystalline anisotropy because of a strain generated at the time of ordering and also has a hard magnetism even when the particle size is reduced.
A typical example of the CuAu type alloy is a FePt alloy. The FePt alloy is a material having the highest magnetocrystalline anisotropy constant. Consequently it is advantageous in reducing the particle size. The FePt alloy can be prepared in various methods. An example of a method for preparation in liquid phase includes a method employing iron carbonyl as an iron precursor, as described in Science, vol. 287, 1989(2000).
This method allows mono-dispersed FePt alloy to be obtain, and is promising in that the resultant particles are self aligned.
However, iron carbonyl is a fatal poison, and the preparation of FePt alloy utilizing such substance as the precursor requires various facilities and steps for safety, such as a ventilating facility and an exhaust gas treating facility, and therefore has inferior productivity.